This invention relates to a trouble detecting unit in an optical security device which is employed for a press or the like.
An optical security device is employed for a press or the like for safety of an operator. In the optical security device, a single or plural light beams are emitted into a hazardous area where an operator may be injured. When the light beams are intercepted by a part of the person, an emergency stop signal is outputted by the device to stop the slide of the press, for instance.
If the light emitting elements adapted to emit light beams, or the light receiving elements adapted to receive the light beams, or their relating circuits become out of order in the above-described conventional optical security device, sometimes it may not work as security means. Therefore, if in such a case the person extends his hand, etc. into the hazardous area, he may lose the hand. A trouble in the optical security system is undoubtedly hazardous to the person.
However, there has been provided no means for detecting the abnormal conditions of the light emitting element, light receiving elements and their relating circuits in the optical security device.